Various methods have been disclosed heretofore for the disposal of sewage sludge. For the past several years, it has been customary in areas along the Eastern Seaboard, and particularly in the New York City area, to load sewage sludge into barges which are towed out to sea and dumped into the ocean. Alternative methods of disposal include dewatering the sewage sludge by the use of centrifuges and dumping the dewatered sewage sludge in and fill areas. Dumping at sea is becoming more and more restricted as a disposal method while, at the same time, metropolitan areas are rapidly running out of available land fill sites.
Incineration of sewage sludge solids has been proposed, but is not an attractive method of disposal due to the water content of moist centrifuged sludges or filter cake solids, which typically contain 65 to 75 weight percent water after concentration by conventional filtering or centrifuging methods.
The process of thin invention is designed to help solve the problem of disposition of sewage sludge by converting dewatered sewage sludge, waste paper, and other municipal solid wastes into usable products without the need for a costly drying process.
In one of its specific embodiments, the product comprises briquettes comprising coal. The art of pressing coal into briquettes is well known. The objective has been principally to utilize coal fines by compacting them into a more easily handled and stored fuel. The compaction or pelleting of municipal refuse, together with waste coal products also has been proposed. Jackman, in U.S. Pat. No. 3,910,775, disclosed the briquetting of coal including coal fines with organic wastes. In this patent, minor quantities of acidic coal fines are apparently used for the purpose of reducing the pH of a sewage stream filtered through the prepared briquettes to precipitate phosphates present in the waste water.
My U.S. Pat. Nos. 4,225,457, 4,152,119, 4,052,173, and 5,125,931, incorporated herein by reference and made a part hereof, disclose the production of briquettes from coal with sewage sludge, and from coal and municipal solid wastes, and their gasification in a moving bed solid fuel gasifier.